New observations and critical assessments of incipient plasticity events and indentation size effect in nanoindentation of ceramic nanocomposites

The ceramic nanocomposites (CNCs) like zirconia toughened alumina (ZTA) ceramics are important futuristic materials for structural and functional applications in advanced strategic systems, structural components, biomedical prostheses and devices. In all structural materials including the ZTA CNCs, the very early stages of plastic deformation i.e., the incipient plasticity events (IPE) are most important to be understood so that the microstructure and mechanical properties can be tuned to suit a given end application. Here we report for the first time the mechanisms of IPE in the nanoindentation experiments conducted at 10–1000 mN loads in the 40 ZTA CNCs. Here 40 ZTA CNC stands for 40 vol% of 3 mol% Yttria partially stabilized zirconia toughened alumina (40ZTA) CNC. The role of load ranges in variations of the IPE related parameters in the 40 ZTA CNCs is also studied. Further, an attempt is made to assess how the amount of zirconia content in ZTA CNCs affects the variations of the IPE related parameters. Through the extensive usage of field emission scanning electron microscopy (FESEM) and theoretical estimations, efforts are also directed to check out the linkage, if any, between the localized shear deformation and/or microcracking with the IPE events that occur in the present CNCs. In addition, a new concept of damage resistance is introduced for the first time in the present work to explain the presence of a strong indentation size effect (ISE) in the 40 ZTA CNCs. Finally, an attempt is also directed to understand how the indentation load (P) controls the relative size of interaction zones of dislocation loops as well as the damage resistance and thereby, engineer the acuteness of the ISE in ZTA CNCs. The implication of these findings in futuristic design of especially the ZTA CNCs for various applications is also discussed.     

高韧性环氧沥青及混合料性能影响因素分析

开发了一种新型高韧性环氧沥青,研究了树脂用量、相容剂种类及用量、高温固化复配体系对高韧性环氧沥青及混合料性能的影响。试验结果表明,随着树脂用量增加,高韧性环氧沥青及混合料的性能随之增强,合适的树脂用量为40%;自制的相容剂能有效改善树脂与基质沥青的相容性,其最佳用量为10%;采用高温固化剂与中温固化剂复配体系,当其用量比为9∶1时,高韧性环氧沥青及混合料能获得良好的力学性能,且常温养护7 d即可形成最终强度。高韧性环氧沥青及混合料具有与进口材料同样优异的性能。     

降低触摸屏玻璃生产难度的组分研究

在Na-Ca-Si玻璃系统中,在保证同样组分和化学强化试验条件的基础上,通过改变不同的Al2O3/SiO2摩尔比,同时结合ZrO2/Al2O3摩尔比的调整,获得提升触摸屏玻璃化学强化效率的组分调整方向,对实际生产具有一定的指导意义。     

国产玻璃绝缘子四十年运行概述

通过试验得出,国产玻璃绝缘子在220kV鸡勃和西柳线路上运行40年的产品机电性能测试值与出厂值相差不大,其中,鸡勃线路上运行40年后的XLP-60玻璃绝缘子的机械破坏负荷试验值为96.42kN(出厂值为98.20kN);工频击穿电压值为170kV(出厂值为153kV);残留机械破坏负荷试验值为68.64kN(出厂值为68.82kN),未出现性能衰减和老化现象。这是由于绝缘子玻璃件中含有钢化内应力(属于永久应力),它不会随产品运行时间的延长而产生衰减。因此,玻璃绝缘子具有寿命周期长和不易老化的特性。     

喷水保护单片钢化玻璃作为防火分隔的有效性实验研究

为了研究喷水保护单片钢化玻璃作为防火分隔的有效性,针对建筑常用的12mm厚单片钢化玻璃,利用木垛火开展了实体建筑模拟火灾实验。实验结果表明,在喷水保护作用下,12mm厚单片钢化玻璃能够起到有效的防火分隔作用。     

FRP加固用结构胶的增韧改性

主要介绍了奇士增韧剂对YJ型环氧树脂浸渍胶的增韧改性。通过对体系微观形貌的观察和测定粘结强度的变化选出合适的增韧剂,并研究了增韧剂不同用量对浸渍胶的粘结性能和各项力学性能的影响,同时对碳纤维复合板增韧前后的老化耐久性能进行了比较。     

超韧无卤阻燃尼龙6防暴服专用料的研制

采用双螺杆挤出加工工艺,通过添加不同组分制得超韧无卤阻燃尼龙(PA)6材料,比较了不同黏度PA6、增韧剂、阻燃剂及加工工艺对材料性能的影响。结果表明,中黏搭配低黏PA6材料可获得最佳的冲击性能和加工性能;在添加15份马来酸酐接枝乙烯–辛烯共聚物增韧剂时增韧效果最好;小粒径、高含量(红磷)红磷母粒的阻燃效果较好且对体系的力学性能影响较小;Mg(OH)2具有很好的协效阻燃和消烟作用,在添加量为3份时效果最佳;适当的螺杆组合可提高体系的阻燃稳定性。     

聚乳酸共混体系的拉伸性能、微观结构及结晶行为

研究了不同含量的丁二醇-己二酸-对苯二甲酸共聚酯(PBAT)与聚丁二酸丁二醇酯(PBS)增韧聚乳酸(PLA)的二元共混体系以及添加LAK粒子(硫酸盐)的三元共混体系拉伸性能、微观结构以及结晶行为,并利用Avrami方程对结晶过程进行了模拟。结果表明,PBAT与PBS的添加都不同程度地改善了PLA的断裂伸长率,在拉伸强度下降较小的前提下大幅度提高了其韧性;LAK粒子能进一步提高PLA-10%PBS二元体系的断裂伸长率;拉伸破坏试样断面的SEM照片表明,两种聚合物界面处以及PLA和粒子之间在外力作用下形成的空洞化是共混体系韧性提高的主要原因;PBAT与PBS的添加均促进了PLA的结晶,PBS还引起了PLA晶型的转变;LAK粒子能够起到成核剂的作用,进一步缩短了两种增韧剂体系的半结晶时间;添加LAK粒子的增韧体系的Avrami方程拟合曲线平行,其成核方式及生长过程相似。     

建筑用钢化玻璃自爆机理及预防措施研究

本文揭示了钢化玻璃及其成套设施在使用过程中存在的安全隐患及其产生原因,提出了控制安全隐患的主要技术措施,研究成果对钢化玻璃自爆伤人事故的预防和控制,具有一定的参考价值。     

Fast preparation of ZTA-TiC-FeCrNi cermets by high-gravity combustion synthesis

ZTA-TiC-FeCrNi cermets are prepared by a fast and furnace-free way called high-gravity combustion synthesis. The synthesized cermet samples show the maximum relative density of 97.6% and a hierarchical microstructure with grain sizes from submicron to >50 µm. The content of TiC has a strong influence on the microstructure and mechanical properties of the cermet samples. A higher TiC content results in refined microstructure, improved hardness, and reduced coefficient of friction. With increasing TiC content, the strength and toughness of the samples first increase and then drops, and reach the maximum of 469±26 MPa and 11.3±0.2 MPa m^1/2 at 20% TiC. Compared with commercial polycrystalline Al₂O₃ ceramics, the ZTA-TiC-FeCrNi cermets exhibit better wear resistance, and the volume loss is lower by one magnitude than Al₂O₃ under the same condition.